1. Field of the Invention
This invention relates to a specimen handling device for collecting, storing, processing and dispensing of samples, and, more specifically, to a device used in the analysis of fecal samples.
2. Background Information
The sampling and testing of fecal specimens for the presence of blood elements, such as hemoglobin or transferrin, provides important information for the early detection and diagnosis of diseases, especially conditions associated with gastrointestinal (GI) bleeding. Such testing detects bleeding that originates anywhere from the mouth to the anus. GI bleeding can be caused by a variety of conditions including infections, duodenal ulcers, carcinomas, polyps, colitis, hemorrhoids and angiomas.
Several methods, including conventional chemical tests and more recent immunoassay tests, have been used to detect occult blood in feces. Tests based on chemical reactions with components of the human occult blood analyte, such as guaiac test and the o-toluidine test, have the inherent problems of false negatives and positives. Such incorrect results arise from cross-reaction of the assay's reagents with degradation products similar to the analytes to be assayed as well as with non-human components that are present due to dietary intake by the patient. For example, the hemoglobin from beef and pork ingested by the patient will also cause a chemical assay to register a (false) positive result. The necessary dietary restrictions imposed on patients to eliminate dietary interference make them inconvenient to use.
By comparison, more recent immunoassays have claimed to solve such diet-based cross-reactivity problems, but many of these tests present a different set of problems. In particular, it has been found that hemoglobin in fecal samples is degraded by the intestinal flora also present in the sample. Sufficient time often lapses between the point that the fecal sample is obtained and the point that the hemoglobin is performed on the sample for the hemoglobin analyte to be degraded by the intestinal flora. For example, Enterobactericae or proteases in a fecal sample will convert hemoglobin to globulin, and the globulin will be undetected by the anti-hemoglobin antibodies in the assay. The degradation causes the assay to render a false negative result.
S. Okuda et al., in U.S. Pat. No. 4,920,045, issued Apr. 24, 1990, herein incorporated by reference, described a two-step approach to solve the problems of hemoglobin-based immunoassays: 1) store the fecal sample in a solution of a glycosidase-type bacteriolytic enzyme until the assay is performed, and 2) also simultaneously detect the human transferrin present in the sample with anti-transferrin antibodies. The glycosidase-type enzyme inhibits the activity of hemoglobin-degrading enzymes in the sample. The transferrin analyte is essentially resistant to such enzymatic degradation.
Thus, for the improved assay such as those of Okuda et al. to work, a sampling device is needed that would immediately bring the fecal sample into contact with a stabilizing solution, and maintaining that contact until the immunoassay is performed. Furthermore, the device should conveniently provide a fixed volume of sample, in order to insure the accuracy of a quantitative or semi-quantitative assay, for example, an immunoassay. As human and veterinary samples often contain infectious biological agents, the device should be designed to prevent human contact with the collected sample during the storage and transportation of the sample, as well as during any further processing of the sample in conjunction with the assay. As a corollary, the device should be economical so as to be disposable, eliminating the need for cleaning and sterilization, and also so as to add a minimum to the total cost of performing the assay. Finally, the device should be simple enough to used by the lay individual in the home, the field, or the like, as trained individuals are usually not the ones who would be using the device. For instance, fecal samples are often collected by the patient in his or her own home. The present invention satisfies these needs and provides related advantages as well.